What I was doing in my reply is called a sumbolic reference?

Symbolic, yes.

And that is deprecated?

No, just frowned upon.

I think it's quite a nice way of getting the value of a variable which name you don't yet know.

It's not. It requires global variables, which suck (see Coping with Scoping) and makes debugging hard. Instead, just use a hash (forget for a moment that the stash is a hash, if you knew that). Your code, using a hash and strict, would be:

use strict;

my %hash;
$hash{the_var_i_want} = "this is the actual value I want to get";
my $the_name = <STDIN>; #say, this would be "the_var\n"
chomp $the_name;
print $hash{"${the_name}_i_want"};
[download]

See also Why it's stupid to `use a variable as a variable name'.